Silencing a piano

[Delwin D Fandrich]

----- Original Message -----
From: "Don" <drose@dlcwest.com>
To: <pianotech@ptg.org>
Sent: September 17, 2001 7:58 AM
Subject: Re: Silencing a piano


> Hi Paul,
>
> Foam rubber is accoustically transparent. I would  recommend ordinary
> fiberglass insulation held in place with a dark tightly woven material.
The
> more glass wool you use the more sound will be absorbed. The factor is 1.6
> for speaker cabinets filled with glass wool (i.e. they appear acoustically
> "bigger" by 1.6 times their interior [cubic] volume)
> --------------------------------------------------------------------------
--

Depending on the density of the glass wool. In an enclosed speaker cabinet
glass wool is used not so much to absorb sound energy as to slow the speed
of sound making the enclosure seem larger than it is and
altering--lowering--it fundamental resonant frequency. In this case you're
trying to attenuate the sound, particularly the sound energy being radiated
directly down toward the floor. Glass wool will work, but it should be
somewhat more dense than typical house insulation. Check the yellow pages
for an industrial insulation supplier and try to find something
approximately twice as dense as house insulation.

The 'tightly woven fabric' holding this in place should be a natural fiber
if possible. Wool is best. Hemp, sisal, etc., should be good, though I've
not seen any test numbers on them. Cotton comes in a poor second to wool,
but ahead of synthetics. Don't use anything like so-called 'speaker cloth'
which is intended to be acoustically transparent. In fact, you might try
something like wool carpet with the fuzzy side up, toward the soundboard.
The idea is to absorb as much energy coming from the bottom of the piano as
possible.

Keep in mind all of this is going to alter the acoustics of the piano.

Personally, I'd try a set of caster cups set on resilient rubber pads all
over a nice thick wool throw rug first and see if the downstairs neighbor
can still hear the 'noise' over his/her TV blasting away at full volume.

Del